kj.'lsltv® Geotechnical Environmental Water Resources Ecological MassDEP RTN 3-23246 Class A-3 Response Action Outcome Partial Statement for 12 Morton Street, Somerville, Massachusetts 50 Tufts Street Site, Somerville, Massachusetts Submitted to: UniFirst Corporation 68 Jons pin Road Wilmington, MA 01887 &C- Submitted by: GEI Consultants, Inc. 3 S*- 400 Unicom Park Drive Woburn, MA 01801 781-721-4000 £>£ > October 21, 2011 Project 04516-3 MassDEP RTN 3-23246 Class A-3 Response Action Outcome Partial Statement for 12 Morton Street, Somerville, Massachusetts 50 Tufts Street Site, Somerville, Massachusetts UniFirst Corporation October 21, 2011 Table of Contents Executive Summary iv 1. Introduction_1^ 1.1 Purpose 1 1.2 Scope 2 1.3 Submittals 2 1.4 Public Record 2 1.5 Contact Information 3 1.6 Conceptual Site Model 3 1.6.1 Property Location and Description 3 1.6.2 Contaminant Distribution 3 2. Property Investigations_5 2.1 Groundwater Sampling 5 2.2 Soil Vapor Sampling 5 2.3 Indoor Air Sampling 6 2.4 Soil Sampling 6 3. EPEM Installation 8 4. Method 3 Risk Characterization_9 4.1 Current and Reasonably Foreseeable Site Activity and Use 9 4.2 Potential Human Receptors 10 4.3 Potential Environmental Receptors 10 4.4 Summary of Analytical Results 10 4.5 “Hot Spot” Evaluation 11 4.6 COPCs 11 4.7 Exposure Pathways 11 4.8 Identification of EPCs 12 4.9 Risk of Harm to Human Health 13 4.10 Risk of Harm to Safety . 13 4.11 Risk of Harm to Public Welfare 13 4.12 Risk of Harm to the Environment 14 4.13 Uncertainty Analysis 14 4.14 Conclusions 14 5. Activity and Use Limitation _15 6. Feasibility of Achieving Background _ 17 GEI Consultants, Inc. n MassDEP RTN 3-23246 Class A-3 Response Action Outcome Partial Statement for 12 Morton Street, Somerville, Massachusetts 50 Tufts Street Site, Somerville, Massachusetts UniFirst Corporation October 21, 2011 7. Source Control 18 8. Representativeness Evaluation and Data Usability Assessment_19 8.1 Conceptual Site Model 19 8.2 Field and Screening Data 19 8.3 Sampling Rationale, Distribution, and Data Completeness 19 8.4 Data Usability Assessment 20 8.5 Data Usability Criteria 20 8.6 Statement of Suitability 20 9. Class A-3 Response Action Outcome Partial Statement_21^ 9.1 Operation, Maintenance, and/or Monitoring 21 10. Limitations 22 Tables 1. Chemical Testing Results - Groundwater 2. Chemical Testing Results - Sub-Slab Soil Vapor 3. Chemical Testing Results - Indoor Air 4. Chemical Testing Results - Soil Figures 1. Site Location Map 2. 12 Morton Street - Portion of Disposal Site Subject to the Class A-3 RAO 3. 12 Morton Street - Exposure Pathway Elimination Measure Details 4. 12 Morton Street - Exposure Pathway Elimination Measure Details Appendices A. MassDEP Transmittal Form (BWSC-104) “Response Action Outcome (RAO) Statement” B. Public Notification Documentation C. Method 3 Risk Characterization D. Activity and Use Limitation E. EPEM Warning Label JDR/ISG:csh N:\04516\19.0 Reports in Progress\19.10 Partial RAOs\Wave 3\12 Morton Street\12 Morton Class A-3 RAO-P.docx GEI Consultants, Inc. in MassDEP RTN 3-23246 Class A-3 Response Action Outcome Partial Statement for 12 Morton Street, Somerville, Massachusetts 50 Tufts Street Site, Somerville, Massachusetts UniFirst Corporation October 21, 2011 Executive Summary On behalf of UniFirst Corporation (UniFirst) of Wilmington, Massachusetts, GEI Consultants, Inc. (GEI) prepared this Class A-3 Response Action Outcome Partial (RAO-P) Statement for 12 Morton Street, Somerville, Massachusetts (the Property), which is a portion of the 50 Tufts Street site (the Site; Fig. 1). The Site is identified by Massachusetts Department of Environmental Protection (MassDEP) Release Tracking Number (RTN) 3-23246. A Site Map that shows the Property in relation to the Site boundary is presented in Fig. 2. This document provides closure for a portion of the Site under the Massachusetts Contingency Plan (MCP; 310 CMR 40.0000) and indicates that a condition of No Significant Risk (NSR) exists at the Property. A release of chlorinated volatile organic compounds (VOCs) to soil and groundwater at the Site was first reported to the MassDEP in 2002. Subsequent investigations at the Site identified chlorinated VOCs, particularly tetrachloroethylene (also called perchloroethylene [PCE]), in indoor air at 50 Tufts Street, and in groundwater and indoor air at residential and commercial properties in the vicinity of 50 Tufts Street, including the Property. To mitigate the vapor intrusion pathway at the Property, GEI installed an Exposure Pathway Elimination Measure (EPEM). In the basement, the EPEM consists of a new concrete floor with vapor sumps installed beneath the concrete and a vapor barrier system covering both the floor and the fieldstone foundation walls, together with a venting system beneath the vapor barrier. Four rounds of indoor air testing conducted after the installation of the EPEM did not detect chlorinated VOCs above laboratory method reporting limits. Based on the post-EPEM indoor air sampling results, the EPEM has mitigated the vapor intrusion pathway and achieved a condition of NSR at the Property. An Activity and Use Limitation (AUL) has been recorded at the Middlesex South District Registry of Deeds requiring the maintenance of the EPEM at the Property to maintain a condition of NSR. A Class A-3 RAO-P Statement is appropriate for the Property based on the following: ■ Remedial actions were conducted and a Permanent Solution has been achieved. ■ A condition of NSR to human health, safety, public welfare, and the environment exists for all receptors. ■ An AUL is required to maintain a condition of NSR. ■ Oil or hazardous material at the Property do not exceed the applicable Upper Concentration Limit in soil or groundwater. GEI Consultants, Inc. iv * .